This invention relates to an optical apparatus for examining an object and in particular but not limited to an optical apparatus for examining carbohydrate constituents in a plant.
Current methods for optically examining objects such as strawberries and other plants require obtaining samples of the objects and examining the samples in laboratories. These methods are inconvenient as the apparatuses for examination cannot be used on the objects in situ or in the fields. They are also destructive as samples must be taken off the objects.
The existing optical apparatuses for the examination do not have the resolution nor the sensitivity which are sufficiently high for reliably examining constituents in fruits or plants in general. They also cannot be easily adapted for examining relative concentrations of the constituents.
These apparatuses have a light source arranged to direct light onto an object and a light detector arranged for detecting reflected or scattered light from the object. The detector must be positioned outside the light path of the source and at some distance from the object in order not to interfere with the light from the source.
The detectors of these prior art apparatuses receive light reflected off the surface of and light scattered from within the object, together with reflected and scattered light from other surfaces. The light received by the detectors therefore include a high degree of noise signals.
The prior art apparatuses also require a relatively high powered light source as a large amount of the light from the source do not reach the target regions of the object.
An object of the present invention is to alleviate or to reduce to a certain degree one or more of the prior art disadvantageous.
In one aspect the present invention resides in an optical apparatus for examining an object. The apparatus comprises a light source adapted to direct a beam of light towards an object under examination, an aperture arranged for receiving the light reflected from, scattered within or passing through the object and, for the beam of light to diverge therefrom means for collimating light arranged so that the beam of light through the aperture incident thereat is collimated. The apparatus also comprises means for dispersing the collimated beam of light from the collimating means into wavelength components, and means for providing electrical output signals which are respectively proportional to energy levels in the wavelength components.
In preference, the apparatus further comprises means for processing the output signals and thereby providing one or more indication signals for respectively indicating one or more characteristics of the object.
An indication means can be arranged for receiving the one or more indication signals and indicating the or each said indication signals in a suitable form. Desirably the indication means is a printer, a display monitor or a combination thereof.
The apparatus may have an interface means to which a computer may be selectively connected thereto for storing the one or more indication signals and/or for further processing the one or more indication signals.
Typically the processing means includes a data correlation device adapted to relate the or each of said indication signals to a characteristic of the object.
The data correlation device may have a set of correlation data for one object or a plurality of sets of correlation data for different types of objects.
Each said characteristic may be any constituent or a relative concentration of any constituent of the object. Examples of the constituents are carbohydrates, starch and sugars including sucrose, glucose, fructose and the like. The characteristic may also relate to any physiological state of the object The physiological states may include growth state, maturity state in plant and the like.
Desirably each said characteristics is a signature of vigour of growth, maturity for picking or any other physiological state of a plant.
Conveniently the data correlation device is removably connectable to the apparatus so that the apparatus can be selectively connected to the data correlation device having a set of correlation data for a particular object under examination.
The data correlation device may conveniently be in the form of a printed circuit card such as a PCMCIA card.
Preferably the output signal providing means includes an detection arrangement for detecting the wavelength components.
It is further preferred that the apparatus has a focusing arrangement for focusing the wavelength components onto the detection arrangement.
The light source may include an illuminator for producing an annulus of light onto the object. The illuminator comprises a hollow body having a reflective interior surface, and one or more lamps disposed so that at least some portions of the light from said one or more lamps are reflected from the reflective surface. The reflective surface is configured so that the light reflected therefrom forms an annulus of light on a region of the object.
In preference said hollow body is substantially conical or half egg shell shaped. The hollow body may also have a substantially parabolic cross section.
Suitably the annulus of light is arranged around a light detection probe for detecting scattered light from said object. The detection probe is suitably positioned along an axis of the hollow body and the light source is positioned at an angle to said axis.
Advantageously the illuminator is provided with a shroud downstream of the light reflected from said reflective surface. In one from the shroud is substantially frusto-conical or curvilinear in shape
The shroud may have a partly or wholly reflective interior surface for redirecting portions of the light from said light source and/or said interior surface of the body to said region of the object.
The shroud may have a rear wall arranged to direct light towards the annulus. The rear wall may be curve shaped or formed as a Fresnel lens.
It is desired that the shroud is removably fixed so that it can be easily replaced. The shroud may be configured for a particularly shaped object. The illuminator can therefore be used for different objects by selecting suitable shrouds for the different objects.
It is also preferred that the apparatus comprises an optical conveying means for conveying the beam of light reflected from or through the object to the aperture. The conveying means may include an optical fibre such as a 500 xcexcm diameter optical fibre with a 11xc2x0 numerical opening. The optical fibre may be arranged within a protective probe.
The aperture can be positioned at about the focal length of the collimating means. It may have one or more parallel slits of a suitable width. In one example the width is 10 xcexcm. Typically the one or more slits are vertically oriented.
Desirably, the position of the collimating means relative to the aperture is adjustable so that the desired resolution and intensity of the apparatus can be easily changed.
Suitably, the collimating means is a collimating lens and typically an achromatic lens.
The dispersing means may include one or more prisms of any suitable configuration. The one or more prisms are preferably equilateral prism(s).
The focusing arrangement may include one or more focusing lenses for focusing the wavelength components onto the detection arrangement. Desirably the one or more focusing lenses are configured so that a linear dispersion of the spectrum can be provided across the detection arrangement. Plano-convex lenses are examples of the focusing lenses.
The detection arrangement preferably includes a plurality of detection elements which provide the electrical output signals in response to detection of the wavelength components.
More preferably the detection elements are arranged in a matrix of at least 2xc3x972 (4) detection elements. Typically the matrix has 32xc3x9732 (2048) or 64xc3x9764 (4096) detection elements.
The detection arrangement conveniently has a charge coupled device (CCD) and the detection elements are in the form of picture elements (pixels).
The light source may be selected from any suitable known sources. It is preferred that the light source is near infrared radiation (NIR).
Desirably, the apparatus has a housing means in which components of the apparatus are located. The housing means may have a substantially light proof first housing member in which the collimating means, the dispersing means and electrical signal providing means are located. The first housing member reduces or eliminates interference from background radiation and reflections from optical surfaces. More desirably the aperture is also located within the first housing member.
More desirably, the housing means is compact so that the apparatus can be used on field or in situ. Typically the housing means is arranged so that in use a user can hold the apparatus in one hand. Alternatively it can be arranged so that it can be worn on a part of the user body such as on a wrist. The housing means may be shaped like a wrist watch, a hand pistol or any other suitable configuration.
The housing means may have a second housing member in which the light source is located and the second housing member has a gap into which at least part of the object can be inserted. It is advantageous that the second, housing member is removably connectable to the first housing member so that the second housing member can be selected from a plurality of second housing members adapted for examining particular kinds of objects.
Where the apparatus is provided with an optical conveying means the conveying means is preferably located in the second housing member.
The first housing member advantageously has the indication means arranged therein. It is also advantageous that the first housing means has the data correlation device removably connected thereto so that the apparatus can be used for different objects.
In one example, the first housing member is shaped like the body of a hand pistol and the second housing member is shaped like a turret of the pistol.
Said reflective surface of the hollow body may be formed according to a method comprises the steps of:
(a) selecting one portion of the reflective interior surface;
(b) calculating the orientation of said portion which will reflect a ray of light from a light source disposed within the hollow body onto the annulus of light in the same axial plane as said ray of light;
(c) stepping to another portion which is in the same vertical plane as said one portion and repeating step (b);
(d) repeating step (c) until said portions can be joined to form a ring; and
(e) repeating steps (a) to (d) for forming another ring adjacent to said ring until the rings extend to a desired area.
Preferably in the step (c) the direction of stepping reverses on completion of half a revolution.
The adjacent portions in each ring may be joined at the intersection of the respective planes containing said adjacent portions, or at about mid way between the intersection and one of said adjacent portions.